Symmetrical DC-link Capacitor Voltage for Cascaded H-Bridge Inverter Supported from Solar PV Array

This paper proposes an algorithm for maintaining symmetrical voltage across H-bridges of cascaded multilevel inverter fed through boost converter in solar photovoltaic system (SPV). During change in environmental conditions such as insolation and temperature, the power across each dc link capacitor changes. It might cause the change in voltage across these capacitors. Because of which the output voltage of cascaded H-bridge inverter becomes asymmetrical. The two or more modules of the H-bridges will have different switching stresses if the voltages across dc link capacitors are asymmetrical. To maintain the symmetrical voltage across capacitors of cascaded multilevel inverter, boost converters is operated according to proposed algorithm. The output of the boost converters with proposed algorithm keeps the voltage symmetrical both under uniform and non-uniform environmental conditions on each SPV array. Carrier phase shifted sinusoidal pulse width modulation is used to operate the multilevel inverter. The proposed algorithm and performance of SPV fed inverter is simulated using power system computer aided design (PSCAD/EMTDC).